Jones, S.

Quinting, Julian

Abstract
Structural changes of a tropical cyclone (TC) during extratropical transition (ET) cause high impact weather. One of the primary goals of the THORPEX-Pacific Asian Regional Campaign (T-PARC) in 2008 was to obtain insights into the various physical processes that account for these structural changes. During this campaign one of the major typhoons in the West Pacific in 2008 -Typhoon Sinlaku- was investigated from tropical cyclogenesis until ET.
As Sinlaku approached the midlatitude baroclinic zone a strong convective system developed in the vicinity of the transitioning typhoon. Research flights with the NRL-P3 and the USAF-C130 aircrafts captured unique observations of the detailed structure of this convective event during ET using the Dual-Doppler-Radar ELDORA and dropsondes. The observational data are assimilated with the recently developed Spline Analysis at Mesoscale Utilizing Radar and Aircraft Instrumentation (SAMURAI) software tool at 4 km horizontal resolution. The obtained SAMURAI analysis enables us to identify deep convection, a stratiform region, warm- and cold frontal structures, and a dry intrusion in the vicinity of the transitioning TC. Q-vector diagnostics indicate that forced ascent in a potentially unstable environment triggers the deep convection.
Strong potential vorticity production by latent heat release within the deep convection leads to a deformation of Sinlaku's wind field and presumably favors the cyclone's decay. Finally, a validation of the ECMWF operational analysis against the SAMURAI analysis identifies remarkable differences with respect to the representation of the convective event.